U.S. patent application number 17/198523 was filed with the patent office on 2021-07-01 for machine tool and electric discharge machining apparatus.
This patent application is currently assigned to Mitsubishi Electric Corporation. The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Hiroki GOTO, Masaharu IMAKI, Kiyoshi ONOHARA, Naoki SUZUKI, Takayuki YANAGISAWA.
Application Number | 20210199424 17/198523 |
Document ID | / |
Family ID | 1000005504028 |
Filed Date | 2021-07-01 |
United States Patent
Application |
20210199424 |
Kind Code |
A1 |
GOTO; Hiroki ; et
al. |
July 1, 2021 |
MACHINE TOOL AND ELECTRIC DISCHARGE MACHINING APPARATUS
Abstract
A machine tool includes a machining unit for feeding cutting oil
to a work surface of a workpiece and machining the work surface, an
optical sensor body unit dividing light outputted from a frequency
sweep light source for outputting light whose frequency varies
periodically into irradiation light with which the workpiece is to
be irradiated and reference light, irradiating the workpiece with
the irradiation light, detecting a peak frequency of interference
light between reflected light which is irradiation light reflected
by the workpiece, and the reference light, and measuring the
distance from the machine tool to the work surface on the basis of
the peak frequency, and a shape calculation unit calculating the
shape of the workpiece on the basis of the distance measured by the
optical sensor body unit.
Inventors: |
GOTO; Hiroki; (Tokyo,
JP) ; ONOHARA; Kiyoshi; (Tokyo, JP) ; IMAKI;
Masaharu; (Tokyo, JP) ; SUZUKI; Naoki; (Tokyo,
JP) ; YANAGISAWA; Takayuki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
Mitsubishi Electric
Corporation
Tokyo
JP
|
Family ID: |
1000005504028 |
Appl. No.: |
17/198523 |
Filed: |
March 11, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2019/036394 |
Sep 17, 2019 |
|
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17198523 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23H 7/32 20130101; G01B
11/2441 20130101; B23H 2500/20 20130101 |
International
Class: |
G01B 11/24 20060101
G01B011/24; B23H 7/32 20060101 B23H007/32 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2018 |
JP |
PCT/JP2018/037409 |
Claims
1. A machine tool including a machining unit for feeding cutting
oil to a work surface of a workpiece and machining the work
surface, the machine tool comprising: an optical sensor unit
dividing light outputted from a frequency sweep light source for
outputting light whose frequency varies periodically into
irradiation light with which the workpiece is to be irradiated and
reference light, irradiating the workpiece with the irradiation
light, detecting a peak frequency of interference light between
reflected light which is irradiation light reflected by the
workpiece, and the reference light, and measuring a distance from
the machine tool to the work surface on a basis of the peak
frequency; and a shape calculation unit calculating a shape of the
workpiece on a basis of the distance measured by the optical sensor
unit.
2. The machine tool according to claim 1, wherein the interference
light contains first interference light which is interference light
between reflected light from the work surface of the workpiece and
the reference light, and second interference light which is
interference light between reflected light from the cutting oil and
the reference light, and the optical sensor unit calculates the
distance from the machine tool to the work surface on a basis of a
peak frequency of the first interference light and a peak frequency
of the second interference light.
3. The machine tool according to claim 2, wherein the optical
sensor unit distinguishes the peak frequency of the first
interference light and the peak frequency of the second
interference light on a basis of magnitude of the peak frequency of
the first interference light and magnitude of the peak frequency of
the second interference light.
4. The machine tool according to claim 3, wherein the optical
sensor unit measures the distance from the machine tool to the work
surface on a basis of both a distance from the machine tool to the
cutting oil and a thickness of the cutting oil.
5. The machine tool according to claim 1, wherein the machining
unit includes: a tool holding unit to hold a machining tool for
machining the work surface; a head body unit to hold the tool
holding unit; and a head drive unit to change a position of the
head body unit relatively with respect to a table on which the
workpiece is placed, and the shape calculation unit calculates the
shape of the workpiece on a basis of both the position of the head
body unit, the position being changed by the head drive unit, and
the distance measured by the optical sensor unit.
6. The machine tool according to claim 1, wherein the machining
unit includes: a tool holding unit to hold a machining tool for
machining the work surface; and a head body unit to hold the tool
holding unit, wherein a part of the optical sensor unit is mounted
on the head body unit.
7. The machine tool according to claim 6, wherein a sensor head
unit having a condensing optical element is mounted, as the part of
the optical sensor unit, on the head body unit.
8. The machine tool according to claim 7, wherein the machine tool
comprises a table having a surface on which the workpiece is
placed, and the sensor head unit is mounted on an outer surface
facing the surface on which the workpiece is placed, out of
multiple outer surfaces which the head body unit has.
9. The machine tool according to claim 1, wherein the machining
unit comprises: a tool holding unit to hold a machining tool for
machining the work surface; and a head body unit to hold the tool
holding unit, wherein a part of the optical sensor unit is held by
the tool holding unit.
10. The machine tool according to claim 9, wherein a sensor head
unit having a condensing optical element is held, as the part of
the optical sensor unit, by the tool holding unit.
11. The machine tool according to claim 1, wherein the machining
unit comprises a tool storage unit storing multiple machining tools
used for machining the work surface, and a part of the optical
sensor unit is stored in the tool storage unit.
12. The machine tool according to claim 1, wherein the machining
unit comprises: a tool holding unit to hold a machining tool for
machining the work surface; and a head body unit to hold the tool
holding unit, wherein the optical sensor unit is held by the tool
holding unit.
13. The machine tool according to claim 1, wherein the machining
unit comprises a tool storage unit storing multiple machining tools
used for machining the work surface, and the optical sensor unit is
stored in the tool storage unit.
14. The machine tool according to claim 1, wherein the machining
unit comprises: a tool holding unit to hold a machining tool for
machining the work surface; and a head body unit to hold the tool
holding unit, wherein a communication cable for outputting
information containing the distance measured by the optical sensor
unit to an outside is passed through an inside of the head body
unit and is led out of the head body unit.
15. The machine tool according to claim 1, wherein the machining
unit comprises a cutting oil nozzle feeding the cutting oil to the
work surface.
16. A machine tool including a machining unit for feeding machining
oil to a work surface of a workpiece, and machining the work
surface, the machine tool comprising: an optical sensor unit
dividing light outputted from a frequency sweep light source for
outputting light whose frequency varies periodically within a
single frequency band into irradiation light with which the
workpiece is to be irradiated and reference light, irradiating the
workpiece with the irradiation light, detecting a peak frequency of
interference light between reflected light which is irradiation
light reflected by the workpiece, and the reference light, and
measuring a distance from the machine tool to the work surface on a
basis of the peak frequency; and a shape calculation unit
calculating a shape of the workpiece on a basis of the distance
measured by the optical sensor unit.
17. An electric discharge machining apparatus including a machining
unit for machining a work surface of a workpiece immersed in
machining oil, the electric discharge machining apparatus
comprising: an optical sensor unit dividing light outputted from a
frequency sweep light source for outputting light whose frequency
varies periodically within a single frequency band into irradiation
light with which the workpiece is to be irradiated and reference
light, irradiating the workpiece with the irradiation light,
detecting a peak frequency of interference light between reflected
light which is irradiation light reflected by the workpiece, and
the reference light, and measuring a distance from the electric
discharge machining apparatus to the work surface on a basis of the
peak frequency; and a shape calculation unit calculating a shape of
the workpiece on a basis of the distance measured by the optical
sensor unit.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of PCT International
Application No. PCT/JP2019/036394, filed on Sep. 17, 2019, which
claims priority under 35 U.S.C. 119(a) to Patent Application No.
PCT/JP2018/037409, filed in Japan on Oct. 5, 2018, all of which are
hereby expressly incorporated by reference into the present
application.
TECHNICAL FIELD
[0002] The present invention relates to a machine tool for and an
electric discharge machining apparatus for machining a work surface
of a workpiece.
BACKGROUND ART
[0003] Conventionally, machine tools that machine an object and
measure the surface shape of a machined work surface of the object
after machining have been known (refer to Patent Literature 1). A
machine tool described in Patent Literature 1 is configured so as
to measure the surface shape of a machined work surface on the
basis of changes in the intensity of reflected light.
[0004] Because an optical sensor cannot receive reflected light
properly in a state in which cutting oil applied at the time of
machining is adhered to the work surface, in the machine tool
described in Patent Literature 1, the cutting oil adhered to the
work surface is removed by blowing the cutting oil off the work
surface before the measurement of the shape.
CITATION LIST
Patent Literature
[0005] Patent Literature 1: JP 2018-36083 A
SUMMARY OF INVENTION
Technical Problem
[0006] However, in order to remove the cutting oil completely, it
is necessary to blow the cutting oil off the work surface for a
long time. In order to shorten the time required to measure the
shape, it is desirable that the surface shape of the work surface
can be measured even in the state in which the cutting oil remains
on the work surface.
[0007] The present invention is made in order to solve the
above-described problem, and it is therefore an object of the
present invention to obtain a machine tool that can measure the
shape of a workpiece even in a case in which cutting oil remains on
a work surface of the workpiece.
Solution to Problem
[0008] A machine tool according to the present invention includes a
machining unit for feeding cutting oil to a work surface of a
workpiece and machining the work surface, and is configured so as
to include: an optical sensor unit for dividing light outputted
from a frequency sweep light source for outputting light whose
frequency varies periodically into irradiation light with which the
workpiece is to be irradiated and reference light, irradiating the
workpiece with the irradiation light, detecting a peak frequency of
interference light between reflected light which is irradiation
light reflected by the workpiece, and the reference light, and
measuring the distance from the machine tool to the work surface on
the basis of the peak frequency; and a shape calculation unit for
calculating the shape of the workpiece on the basis of the distance
measured by the optical sensor unit.
Advantageous Effects of Invention
[0009] The machine tool according to the present invention can
measure the shape of the workpiece even in a case in which cutting
oil remains on the work surface of the workpiece.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a schematic diagram showing a machine tool
according to Embodiment 1;
[0011] FIG. 2 is a schematic diagram showing an optical sensor unit
20 according to Embodiment 1;
[0012] FIG. 3 is an explanatory drawing showing an example of
frequency sweep light;
[0013] FIG. 4 is an explanatory drawing showing the reflection of
irradiation light on a work surface 3a, and the reflection of the
irradiation light on cutting oil;
[0014] FIG. 5 is a hardware block diagram of a computer in a case
in which a distance calculation unit 40 is implemented by software,
firmware, or the like;
[0015] FIG. 6 is a schematic diagram showing a control unit 50 of
the machine tool according to Embodiment 1;
[0016] FIG. 7A is an explanatory drawing showing an initial
distance L.sub.0 which is the distance from a leading end 21a of a
sensor head unit 21 to the position of a work surface 3a in a state
in which no machining of the work surface 3a is performed;
[0017] FIG. 7B is an explanatory drawing showing a distance L from
the leading end 21a of the sensor head unit 21 to the position of
the work surface 3a in a state in which machining of the work
surface 3a has been performed;
[0018] FIG. 8 is a hardware block diagram showing the hardware of a
part of the control unit 50;
[0019] FIG. 9 is a hardware block diagram of a computer in a case
in which a part of the control unit 50 is implemented by software,
firmware, or the like;
[0020] FIG. 10 is a flowchart showing a procedure when the machine
tool measures the shape of a work surface 3a of a workpiece 3;
[0021] FIG. 11 is a flowchart showing a process of calculating the
distance in a sensor body unit 22;
[0022] FIG. 12 is an explanatory drawing showing an example of
signals in a frequency domain;
[0023] FIG. 13 is a schematic diagram showing a machine tool
according to Embodiment 2;
[0024] FIG. 14 is a schematic diagram showing a sensor head unit
21b of Embodiment 2;
[0025] FIG. 15 is a block diagram showing a machine tool according
to Embodiment 3;
[0026] FIG. 16 is a schematic diagram showing a machine tool
according to Embodiment 4;
[0027] FIG. 17 is a partly enlarged view showing the machine tool
according to Embodiment 4; and
[0028] FIG. 18 is a schematic diagram showing a machine tool
according to Embodiment 5.
DESCRIPTION OF EMBODIMENTS
[0029] Hereinafter, in order to explain the present invention in
greater detail, embodiments of the present invention will be
described with reference to the accompanying drawings.
Embodiment 1
[0030] FIG. 1 is a schematic diagram showing a machine tool
according to Embodiment 1. In FIG. 1, a table 1 is a base on which
a workpiece 3 which is an object to be machined is placed. Vices 2
are fixtures for fixing the workpiece 3 so that the workpiece 3
does not move at the time of machining the workpiece 3. The
workpiece 3 is a piece of metal or the like whose work surface 3a
is to be machined by a machining unit 10. In Embodiment 1, for the
sake of simplicity of the explanation, it is assumed that the work
surface 3a before machining by the machining unit 10 is plane.
[0031] The machining unit 10 includes a machining head 11, a
machining tool 12, a head drive unit 13, and a cutting oil nozzle
14. The machining unit 10 feeds cutting oil to the work surface 3a
of the workpiece 3, and machines the work surface 3a.
[0032] The machining head 11 includes a head body unit 11a and a
spindle 11b which is a tool holding unit. The head body unit 11a is
a metallic structure for supporting the spindle 11b. The spindle
11b is a metallic shaft-shaped part which includes a
not-illustrated chuck device for attachably/detachably holding the
machining tool 12 and which rotationally moves in a state of
holding the machining tool 12. Further, a sensor head unit 21 which
is a part of an optical sensor unit 20 is mounted on the head body
unit 11a.
[0033] The machining tool 12 is a cutting tool for cutting the work
surface 3a of the workpiece 3 through its rotating operation, and
is an edged tool for metal processing, such as a milling cutter, an
end mill, a drill, or a tap.
[0034] The head drive unit 13 is a drive mechanism for relatively
changing the position of the head body unit 11a with respect to the
work surface 3a in accordance with a control signal outputted from
a control unit 50. The direction of the change of the position of
the head body unit 11a, the change being performed by the head
drive unit 13, is the x-axis direction, the y-axis direction, or
the z-axis direction which is shown in FIG. 1.
[0035] The cutting oil nozzle 14 applies the cutting oil to the
work surface 3a of the workpiece 3 when receiving an instruction to
feed the cutting oil from the control unit 50.
[0036] The optical sensor unit 20 includes the sensor head unit 21,
a sensor body unit 22, and an optical transmission unit 23. The
optical sensor unit 20 is a sensor for calculating the distance
from a leading end 21a of the sensor head unit 21 to the work
surface 3a machined by the machining unit 10.
[0037] The sensor head unit 21 is mounted on an outer surface 11c
facing the table 1, out of multiple outer surfaces which the head
body unit 11a has. The sensor head unit 21 emits irradiation light
outputted from the sensor body unit 22 toward the work surface 3a,
and receives reflected light containing both reflected light which
is irradiation light reflected by the work surface 3a and reflected
light which is irradiation light reflected by the cutting oil. The
sensor head unit 21 outputs the reflected light received thereby to
the sensor body unit 22.
[0038] The sensor body unit 22 calculates the distance from the
leading end 21a of the sensor head unit 21 to the work surface 3a,
and outputs distance information showing the calculated distance to
the control unit 50.
[0039] The optical transmission unit 23 is a transmission path for
light heading for the sensor head unit 21 from the sensor body unit
22, and light heading for the sensor body unit 22 from the sensor
head unit 21, and includes an optical fiber. Although in the
machine tool of Embodiment 1 the optical transmission unit 23 is
disposed, the optical transmission unit 23 is not necessarily
needed. In the case in which the optical transmission unit 23 is
not disposed, light can be transmitted via space.
[0040] The control unit 50 outputs a control signal showing the
position to which the head body unit 11a is to be moved to the head
drive unit 13, and outputs an instruction to feed the cutting oil
to the cutting oil nozzle 14. The control unit 50 calculates the
shape of the work surface 3a from both the position of the head
body unit 11a, the position being changed by the head drive unit
13, and the distance represented by the distance information
outputted from the sensor body unit 22.
[0041] Next, the configuration of the optical sensor unit 20 will
be explained using FIG. 2. FIG. 2 is a schematic diagram showing
the optical sensor unit 20 according to Embodiment 1. The optical
sensor unit 20 includes a frequency sweep light output unit 31, an
optical dividing unit 32, an optical interference unit 36, an
analog to digital converter (referred to as an "A/D converter"
hereinafter) 39, and a distance calculation unit 40, as shown in
FIG. 2.
[0042] In FIG. 2, the frequency sweep light output unit 31 includes
a frequency sweep light source 31a for outputting frequency sweep
light whose frequency varies with time within a single frequency
band. The single frequency band ranges from a minimum frequency
f.sub.MIN to a maximum frequency F.sub.max. The frequency sweep
light output unit 31 outputs the frequency sweep light to the
optical dividing unit 32. FIG. 3 is an explanatory drawing showing
an example of the frequency sweep light. The frequency sweep light
is a signal whose frequency varies from the minimum frequency
f.sub.min to the maximum frequency f.sub.max with time. When the
frequency of the frequency sweep light reaches the maximum
frequency f.sub.max, the frequency returns to the minimum frequency
f.sub.min at that time and, after that, varies from the minimum
frequency f.sub.min to the maximum frequency f.sub.max again. The
frequency sweep light may be referred to as chirp signal light.
[0043] The optical dividing unit 32 includes an optical coupler 33
and a circulator 34. The optical coupler 33 is a light dividing
element for dividing the frequency sweep light outputted from the
frequency sweep light output unit 31 into reference light and
irradiation light. The optical coupler 33 outputs the reference
light to an optical interferometer 37 and outputs the irradiation
light to the circulator 34.
[0044] The circulator 34 outputs the irradiation light outputted
from the optical coupler 33 to a condensing optical element 35 of
the sensor head unit 21 via the optical transmission unit 23.
Further, the circulator 34 outputs the reflected light outputted
from the condensing optical element 35 to the optical
interferometer 37.
[0045] The sensor head unit 21 has the condensing optical element
35. The condensing optical element 35 condenses the irradiation
light outputted from the circulator 34 onto the work surface 3a.
Concretely, the condensing optical element 35 includes two aspheric
lenses, and forms the light outputted from the circulator 34 into
collimated light by using a previous-stage aspheric lens and, after
that, condenses the collimated light by using a next-stage aspheric
lens and applies the condensed light to the work surface 3a.
[0046] FIG. 4 is an explanatory drawing showing the reflection of
the irradiation light on the work surface 3a and the reflection of
the irradiation light on the cutting oil. The irradiation light
outputted from the condensing optical element is not only reflected
by the work surface 3a, but also reflected by the cutting oil, as
shown in FIG. 4.
[0047] Returning to FIG. 2, the condensing optical element 35
receives the reflected light containing both the reflected light
from the work surface 3a and the reflected light from the cutting
oil. The condensing optical element 35 outputs the reflected light
received thereby to the circulator 34 via the optical transmission
unit 23. The circulator 34 outputs the reflected light outputted
from the condensing optical element to the optical interferometer
37.
[0048] The optical interference unit 36 includes the optical
interferometer 37 and an optical detector 38. The optical
interference unit 36 generates interference light between the
reflected light received by the sensor head unit 21 and the
reference light, and converts the interference light into an
electric signal and outputs the electric signal to the A/D
converter 39.
[0049] The reflected light outputted from the circulator 34 and the
reference light outputted from the optical coupler 33 are made to
be incident on the optical interferometer 37. The optical
interferometer 37 generates interference light between the
reflected light and the reference light. Because the reflected
light from the workpiece contains the reflected light from the work
surface 3a and the reflected light from the cutting oil as
described above, the interference light generated by the optical
interferometer 37 also contains work surface interference light
(first interference light) which is interference light between the
reflected light from the work surface 3a and the reference light,
and cutting oil interference light (second interference light)
which is interference light between the reflected light from the
cutting oil and the reference light.
[0050] The optical detector 38 detects the interference light
containing both the work surface interference light and the cutting
oil interference light, and converts the interference light into an
electric signal. The optical detector 38 outputs the electric
signal to the A/D converter 39.
[0051] The A/D converter 39 converts the electric signal outputted
from the optical detector 38 from an analog signal into a digital
signal, and outputs the digital signal to the distance calculation
unit 40.
[0052] The distance calculation unit 40 analyzes the frequencies of
the interference light generated by the optical interference unit
36 by converting the digital signal outputted from the A/D
converter 39 into signals in a frequency domain, and calculates a
distance L from the leading end 21a of the sensor head unit 21 to
the work surface 3a on the basis of a result of the analysis of the
frequencies. Concretely, the distance calculation unit
distinguishes between the frequency of the work surface
interference light and the frequency of the cutting oil
interference light, and calculates the distance L from the leading
end 21a of the sensor head unit 21 to the work surface 3a on the
basis of the frequency of the work surface interference light. The
distance calculation unit 40 outputs distance information showing
the calculated distance L to a shape calculation unit 75 of the
control unit 50.
[0053] The distance calculation unit 40 is implemented by, for
example, a distance calculation circuit not illustrated. The
distance calculation circuit is, for example, a single circuit, a
composite circuit, a programmable processor, a parallel
programmable processor, an application specific integrated circuit
(ASIC), a field-programmable gate array (FPGA), or a combination of
these circuits.
[0054] Further, although the example in which the distance
calculation unit 40 is implemented by the distance calculation
circuit which is hardware for exclusive use is shown here, no
limitation is intended to this example, and the distance
calculation unit may be implemented by software, firmware, or a
combination of software and firmware. The software or the firmware
is stored as a program in a memory of a computer. The computer
refers to hardware that executes a program, and includes, for
example, a central processing unit (CPU), a central processing
device, a processing device, an arithmetic device, a
microprocessor, a microcomputer, a processor, or a digital signal
processor (DSP). FIG. 5 is a hardware block diagram of the computer
in the case in which the distance calculation unit 40 is
implemented by software, firmware, or the like. In the case in
which the distance calculation unit is implemented by software,
firmware, or the like, a program for causing the computer to
perform a processing procedure of the distance calculation unit 40
is stored in a memory 61. A processor 62 of the computer then
executes the program stored in the memory 61.
[0055] Next, the configuration of the control unit 50 will be
explained using FIG. 6. FIG. 6 is a schematic diagram showing the
control unit 50 of the machine tool according to Embodiment 1.
[0056] An input unit 71 receives an instruction from a user to feed
the cutting oil, an instruction from a user to machine the
workpiece 3, an instruction from a user to measure the shape of the
workpiece 3, or the like. The input unit 71 is implemented by a
man-machine interface such as operation buttons.
[0057] A storage device 72 stores shape data showing the target
shape of the work surface 3a. The shape data contains data showing
the coordinate values (x, y) of each of multiple points on the work
surface 3a and data showing depth information d about each of the
multiple points. The depth information d shows a cutting depth from
the plane which is the work surface 3a in a state in which no
machining is yet performed. The target shape is, for example,
designed by a user as the shape of the work surface 3a after the
machining. The storage device 72 is implemented by, for example, a
hard disc.
[0058] When an instruction to machine the workpiece 3 or an
instruction to measure the shape of the workpiece 3 is received by
the input unit 71, a coordinate value setting unit 73 acquires the
shape data stored in the storage device 72. The coordinate value
setting unit 73 generates a control signal showing the position to
which the head body unit 11a is to be moved on the basis of the
acquired shape data. The movement position of the head body unit
11a is expressed by coordinate values (x, y).
[0059] When an instruction to machine the workpiece 3 is received
by the input unit 71, the control signal generated by the
coordinate value setting unit 73 contains the depth information d
about the point expressed by the coordinate values (x, y). The head
drive unit 13 moves the head body unit 11a to the movement position
represented by the control signal generated by the coordinate value
setting unit 73 and, after that, moves the head body unit 11a along
the z-axis direction on the basis of the depth information d.
[0060] On the other hand, when an instruction to measure the shape
of the workpiece 3 is received by the input unit 71, the control
signal generated by the coordinate value setting unit 73 contains,
for example, information for moving the position in the z-axis
direction of the head body unit 11a to a reference position. The
reference position is the position of the head body unit 11a in the
z-axis direction at the time of measuring the shape of the work
surface 3a, and is given in the coordinate value setting unit 73.
When the head body unit 11a is located at the reference position,
the distance from the leading end 21a of the sensor head unit 21 to
the position of the work surface 3a is L.sub.0, as shown in FIG.
7A, and L.sub.0 is referred to as the initial distance hereinafter.
The initial distance L.sub.0 is also given in the coordinate value
setting unit 73. FIG. 7A is an explanatory drawing showing the
initial distance L.sub.0 which is the distance from the leading end
21a of the sensor head unit 21 to the position of the work surface
3a in a state in which no machining of the work surface 3a is
performed. FIG. 7B is an explanatory drawing showing the distance L
from the leading end 21a of the sensor head unit 21 to the position
of the work surface 3a in a state in which machining of the work
surface 3a has been performed.
[0061] Returning to FIG. 6, the head drive unit 13 which has
received the control signal moves the head body unit 11a to the
movement position represented by the control signal generated by
the coordinate value setting unit 73 and, after that, moves the
head body unit 11a along the z-axis direction in such away that the
position of the head body unit 11a in the z-axis direction becomes
the reference position.
[0062] Further, when an instruction to measure the shape of the
workpiece 3 is received by the input unit 71 and a control signal
is transmitted to the head drive unit 13, the coordinate value
setting unit 73 transmits a synchronization signal, which is a
trigger for causing frequency sweep light to be emitted from the
frequency sweep light source 31a, to the sensor body unit 22. In
addition, when an instruction to measure the shape of the workpiece
3 is received by the input unit 71, the coordinate value setting
unit 73 outputs the shape data and the initial distance L.sub.0 to
each of the shape calculation unit 75 and an error calculation unit
76.
[0063] When an instruction to feed the cutting oil is received by
the input unit 71, a cutting oil feed unit 74 outputs an
instruction to feed the cutting oil, the instruction showing that
the cutting oil is to be applied to the work surface 3a, to the
cutting oil nozzle 14.
[0064] The shape calculation unit 75 calculates the difference
between the initial distance L.sub.0 outputted from the coordinate
value setting unit 73 and the distance L represented by the
distance information outputted from the distance calculation unit
40, as a cutting depth .DELTA.L (=L-L.sub.0) of the work surface
3a. The shape calculation unit 75 outputs data containing both the
data showing the coordinate values (x, y) of each of the multiple
points and the cutting depth .DELTA.L, which are contained in the
shape data, as data (x, y, .DELTA.L) showing the shape of the work
surface 3a, to each of the error calculation unit 76 and a
three-dimensional data conversion unit 78.
[0065] The error calculation unit 76 calculates an error .DELTA.d
between the shape calculated by the shape calculation unit 75 and
the target shape of the work surface 3a. For example, the error
calculation unit 76 compares the shape data (x, y, d) outputted
from the coordinate value setting unit 73 and the data (x, y,
.DELTA.L) outputted from the shape calculation unit 75 and showing
the shape, and calculates an error .DELTA.d (=d-.DELTA.L) in the
z-axis direction of each of the multiple points on the work surface
3a. The error calculation unit 76 outputs error information showing
the error .DELTA.d in the z-axis direction of each of the multiple
points to a display 79.
[0066] A display processing unit 77 includes the three-dimensional
data conversion unit 78 and the display 79.
[0067] The three-dimensional data conversion unit 78 converts the
data (x, y, .DELTA.L) outputted from the shape calculation unit 75
into three-dimensional data, and causes the display 79 to display
the work surface 3a in three dimensions in accordance with the
three-dimensional data. The three-dimensional data is used for
three-dimensional rendering.
[0068] The display 79 is implemented by, for example, a liquid
crystal display. The display 79 displays the work surface 3a in
three dimensions, and also displays the error .DELTA.d represented
by the error information outputted from the error calculation unit
76.
[0069] FIG. 8 is a hardware block diagram showing the hardware of a
part of the control unit 50. As shown in FIG. 8, the coordinate
value setting unit 73 is implemented by a coordinate value setting
circuit 81, the cutting oil feed unit 74 is implemented by a
cutting oil feed circuit 82, the shape calculation unit 75 is
implemented by a shape calculation circuit 83, the error
calculation unit 76 is implemented by an error calculation circuit
84, and the three-dimensional data conversion unit 78 is
implemented by a three-dimensional data conversion circuit 85.
[0070] Here, it is assumed that each of the following units: the
coordinate value setting unit 73, the cutting oil feed unit 74, the
shape calculation unit 75, the error calculation unit 76, and the
three-dimensional data conversion unit 78, which are the components
of the part of the control unit 50, is implemented by hardware for
exclusive use as shown in FIG. 8. More specifically, the example in
which the part of the control unit 50 is implemented by the
coordinate value setting circuit 81, the cutting oil feed circuit
82, the shape calculation circuit 83, the error calculation circuit
84, and the three-dimensional data conversion circuit 85 is shown.
However, no limitation is intended to this example, and a part of
the control unit 50 may be implemented by software, firmware, or a
combination of software and firmware.
[0071] FIG. 9 is a hardware block diagram of a computer in the case
in which the part of the control unit 50 is implemented by
software, firmware, or the like. In the case in which the part of
the control unit 50 is implemented by software, firmware, or the
like, programs for causing the computer to perform processing
procedures of the coordinate value setting unit 73, the cutting oil
feed unit 74, the shape calculation unit 75, the error calculation
unit 76, and the three-dimensional data conversion unit 78 are
stored in a memory 91. A processor 92 of the computer executes the
programs stored in the memory 91.
[0072] Next, the operation of the machine tool according to
Embodiment 1 will be explained. First, the operation at the time
that the machine tool cuts the work surface 3a of the workpiece 3
will be explained. Because the operation of cutting the work
surface 3a is well known, the operation of cutting the work surface
3a will be explained briefly hereinafter.
[0073] The input unit 71 receives an instruction to feed the
cutting oil from a user. When the input unit 71 receives an
instruction to feed the cutting oil, the cutting oil feed unit 74
outputs an instruction to feed the cutting oil, this instruction
showing that the cutting oil is to be applied to the work surface
3a, to the cutting oil nozzle 14. When receiving the instruction to
feed the cutting oil from the cutting oil feed unit 74, the cutting
oil nozzle 14 applies the cutting oil to the work surface 3a.
[0074] The input unit 71 receives an instruction to machine the
workpiece 3 from the user. When the input unit 71 receives the
instruction to machine, the coordinate value setting unit 73
acquires the shape data stored in the storage device 72.
[0075] The coordinate value setting unit 73 generates a control
signal showing the position to which the head body unit 11a is to
be moved on the basis of the shape data, and outputs the control
signal to the head drive unit 13. Concretely, the coordinate value
setting unit 73 selects one point from the multiple points on the
work surface 3a, generates a control signal for moving the head
body unit 11a to the coordinate values (x, y) of the one point
selected, and outputs the control signal to the head drive unit 13.
Then, when the cutting at the one point selected is completed, the
coordinate value setting unit 73 selects one point at which the
cutting is not completed yet, generates a control signal for moving
the head body unit 11a to the coordinate values (x, y) of the one
point selected, and outputs the control signal to the head drive
unit 13. The coordinate value setting unit 73 repeatedly generates
a control signal for moving the head body unit 11a until the
cutting at all the points on the work surface 3a is completed.
[0076] Every time receiving a control signal from the coordinate
value setting unit 73, the head drive unit 13 moves the head body
unit 11a to the movement position represented by the control signal
and, after that, moves the head body unit 11a along the z-axis
direction on the basis of the depth information d contained in the
control signal. The machining tool 12 held by the head body unit
11a cuts the work surface 3a through, for example, the rotating
operation of the spindle 11b.
[0077] Here, when the input unit 71 receives an instruction to
machine the workpiece 3 from a user, the cutting oil feed unit 74
outputs an instruction to feed the cutting oil to the cutting oil
nozzle 14. However, this is only an example, and, for example, the
cutting oil feed unit 74 may output an instruction to feed the
cutting oil to the cutting oil nozzle 14 at fixed time intervals.
As an alternative, a sensor for detecting the presence or absence
of the cutting oil on the work surface 3a may be provided, and when
the sensor detects that there is no cutting oil, the cutting oil
feed unit 74 may output an instruction to feed the cutting oil to
the cutting oil nozzle 14.
[0078] Further, here, when the input unit 71 receives an
instruction to machine the workpiece 3 from a user, the coordinate
value setting unit 73 outputs a control signal to the head drive
unit 13. However, this is only an example, and, for example, when
an instruction to machine the workpiece 3 is received from the
outside, the coordinate value setting unit 73 may output a control
signal to the head drive unit 13. As an alternative, the coordinate
value setting unit 73 may output a control signal to the head drive
unit 13 in accordance with a program stored in an internal
memory.
[0079] Next, the operation at the time that the machine tool
measures the shape of the work surface 3a of the workpiece 3 will
be explained. FIG. 10 is a flowchart showing a procedure at the
time that the machine tool measures the shape of the work surface
3a of the workpiece 3.
[0080] The input unit 71 receives an instruction to measure the
shape of the workpiece 3 from a user. When the input unit 71
receives an instruction to measure the shape, the coordinate value
setting unit 73 acquires the shape data stored in the storage
device 72. The coordinate value setting unit 73 generates a control
signal showing the position to which the head body unit 11a is to
be moved on the basis of the shape data, and outputs the control
signal to each of the following units: the head drive unit 13 and
the sensor body unit 22 (step ST1). Concretely, the coordinate
value setting unit 73 selects one point from the multiple points on
the work surface 3a, generates a control signal for moving the head
body unit 11a to the coordinate values (x, y) of the one point
selected, and outputs the control signal to the head drive unit 13.
The coordinate value setting unit 73 also outputs a synchronization
signal to the sensor body unit 22 (step ST1).
[0081] When measurement of the distance with respect to the one
point selected is completed, the coordinate value setting unit 73
selects one point on which measurement is not completed yet,
generates a control signal for moving the head body unit 11a to the
coordinate values (x, y) of the one point selected, and outputs the
control signal to each of the head drive unit 13 and the sensor
body unit 22. The coordinate value setting unit 73 repeatedly
generates a control signal for moving the head body unit 11a until
measurement of the distances with respect to all the points on the
work surface 3a is completed.
[0082] Each control signal generated by the coordinate value
setting unit 73 contains information for moving the position in the
z-axis direction of the head body unit 11a to the reference
position. When receiving a control signal from the coordinate value
setting unit 73, the head drive unit 13 moves the head body unit
11a to the movement position represented by the control signal and,
after that, moves the position in the z-axis direction of the head
body unit 11a to the reference position (step ST2).
[0083] When receiving a notification showing that the movement is
completed from the head drive unit 13 after receiving the
synchronization signal from the coordinate value setting unit 73,
the sensor body unit 22 starts the process of measuring the
distance and calculates the distance L from the leading end 21a of
the sensor head unit 21 to the work surface 3a (step ST3).
[0084] Hereinafter, the process of calculating the distance in the
sensor body unit 22 will be explained concretely using FIG. 11.
FIG. 11 is a flowchart showing the process of calculating the
distance in the sensor body unit 22.
[0085] When receiving a notification showing that the movement is
completed from the head drive unit 13 after receiving the
synchronization signal from the coordinate value setting unit 73,
the frequency sweep light output unit 31 outputs the frequency
sweep light whose frequency varies with time to the optical coupler
33 (step ST31).
[0086] The frequency sweep light is divided into reference light
and irradiation light by the optical coupler 33, and the
irradiation light is outputted to the circulator 34 and the
reference light is outputted to the optical interferometer 37. The
irradiation light is made to be incident on the condensing optical
element 35 via the circulator 34 and the optical transmission unit
23, and is condensed onto the work surface 3a by the condensing
optical element 35.
[0087] Reflected light is made to be incident on the optical
interferometer 37 via the condensing optical element 35, the
optical transmission unit 23, and the circulator 34. The reflected
light outputted from the circulator 34 and the reference light
outputted from the optical coupler 33 interfere with each other at
the optical interferometer 37, and the interference light is
outputted to the optical detector 38.
[0088] The optical detector 38 detects the interference light
outputted from the optical interferometer 37 (step ST32). The
optical detector 38 converts the interference light into an
electric signal and outputs this electric signal to the A/D
converter 39.
[0089] When receiving the electric signal from the optical detector
38, the A/D converter 39 converts the electric signal from an
analog signal into a digital signal (step ST33) and outputs the
digital signal to the distance calculation unit 40.
[0090] When receiving the digital signal from the A/D converter 39,
the distance calculation unit 40 converts the digital signal into
signals in the frequency domain, as shown in FIG. 12, by, for
example, performing the fast Fourier transform (FFT) on the digital
signal. FIG. 12 is an explanatory drawing showing an example of the
signals in the frequency domain.
[0091] The distance calculation unit 40 compares the amplitudes of
the signals in the frequency domain and a threshold Th, and detects
the frequency of a signal whose amplitude is greater than the
threshold Th, out of the signals in the frequency domain, as a peak
frequency. Because the interference light detected by the optical
detector 38 contains the work surface interference light and the
cutting oil interference light as described above, a peak frequency
f.sub.1 corresponding to the work surface interference light and t
peak frequency f.sub.2 corresponding to the cutting oil
interference light are detected. The threshold Th is stored in an
internal memory of the distance calculation unit 40. The threshold
Th may be provided to the distance calculation unit 40 from the
outside.
[0092] Here, because the distance from the leading end 21a of the
sensor head unit 21 to the cutting oil is shorter than the distance
from the leading end 21a of the sensor head unit 21 to the work
surface 3a, the magnitude of the peak frequency f.sub.2 is lower
than the magnitude of the peak frequency f.sub.1. Namely, the
following inequality: f.sub.1>f.sub.2 is established.
[0093] When the peak frequency f.sub.1 and the peak frequency
f.sub.2 are detected, the distance calculation unit 40 recognizes
that the higher one of the peak frequencies f.sub.1 and f.sub.2 is
the frequency of the work surface interference light and the lower
one of the peak frequencies is the frequency of the cutting oil
interference light.
[0094] The distance calculation unit 40 calculates the distance L
from the leading end 21a of the sensor head unit 21 to the work
surface 3a (=L.sub.Oil+L.sub.Depth) on the basis of the peak
frequency f.sub.1 which is the frequency of the work surface
interference light and the frequency f.sub.2 of the cutting oil
interference light (step ST34).
[0095] A process of calculating the distance L.sub.Oil from the
sensor head unit 21 to the cutting oil using the peak frequency
f.sub.2 is expressed by equation (1). In equation (1), the velocity
of light is denoted by c, the sweep time of the frequency sweep
light source 31a is denoted by .DELTA..tau., the sweep band of the
frequency sweep light source is denoted by .DELTA.v, and a
reference frequency at the time that the distance from the sensor
head unit 21 is the given distance L.sub.0 is denoted by
f.sub.0.
L oil = c ( f 2 - f 0 ) .DELTA..tau. 2 .DELTA. v + L 0 ( 1 )
##EQU00001##
[0096] A process of calculating the thickness L.sub.Depth of the
cutting oil is expressed by equation (2) on the basis of the
difference between the peak frequency f.sub.1 and the peak
frequency f.sub.2, the refractive index n of the cutting oil, the
velocity of light c, and the sweep time .tau..tau. and the sweep
band Av of the frequency sweep light source 31a.
L Depth = c ( f 1 - f 2 ) .DELTA..tau. 2 n .DELTA. v ( 2 )
##EQU00002##
[0097] The distance calculation unit 40 outputs distance
information showing the distance L to the shape calculation unit 75
of the control unit 50 (step ST35).
[0098] Returning to FIG. 10, the shape calculation unit 75
calculates the difference between the initial distance L.sub.0
outputted from the coordinate value setting unit 73 and the
distance L represented by the distance information outputted from
the distance calculation unit 40 as the cutting depth .DELTA.L of
the work surface 3a (refer to FIG. 7B), as shown in the following
equation (3) (step ST4).
.DELTA.L=L-L.sub.0 (3)
[0099] The shape calculation unit 75 extracts the data showing the
coordinate values (x, y) of each of the multiple points on the work
surface 3a from the shape data (x, y, d) outputted from the
coordinate value setting unit 73 and showing the target shape.
[0100] The shape calculation unit 75 outputs data containing both
the extracted data showing the coordinate values (x, y) of each of
the multiple points, and the cutting depth .DELTA.L, as the data
(x, y, .DELTA.L) showing the shape of the work surface 3a, to each
of the error calculation unit 76 and the three-dimensional data
conversion unit 78.
[0101] The error calculation unit 76 acquires both the shape data
(x, y, d) outputted from the coordinate value setting unit 73 and
showing the target shape, and the data (x, y, .DELTA.L) outputted
from the shape calculation unit 75 and showing the shape. The error
calculation unit 76 compares the shape data (x, y, d) showing the
target shape and the data (x, y, .DELTA.L), and calculates an error
.DELTA.d in the z-axis direction of each of the multiple points on
the work surface 3a, as shown in the following equation (4) (step
ST5). The error .DELTA.d is the error between the cutting depth of
the work surface 3a in the target shape and the cutting depth of
the work surface 3a after the machining.
.DELTA.d=d-.DELTA.L (4)
[0102] The error calculation unit 76 outputs error information
showing the error .DELTA.d in the z-axis direction of each of the
multiple points to the display 79.
[0103] When receiving the data (x, y, .DELTA.L) showing the shape
from the shape calculation unit 75, the three-dimensional data
conversion unit 78 stores the data (x, y, .DELTA.L). The
three-dimensional data conversion unit 78 stores the pieces of data
(x, y, .DELTA.L) about all the points on the work surface 3a.
[0104] The three-dimensional data conversion unit 78 converts the
pieces of data (x, y, .DELTA.L) about all the points on the work
surface 3a into pieces of three-dimensional data, and causes the
display 79 to display the work surface 3a in three dimensions in
accordance with the pieces of three-dimensional data. Each
three-dimensional data is used for three-dimensional rendering.
[0105] The display 79 displays the work surface 3a in three
dimensions and also displays the error .DELTA.d represented by each
of the pieces of error information outputted from the error
calculation unit 76 (step ST6). By referring to the display 79
displaying the error Id, the user can check, for example, whether
or not the machining of the workpiece 3 by the machine tool has
been performed properly.
[0106] Here, when the input unit 71 receives an instruction to
measure the shape of the workpiece 3 from a user, the coordinate
value setting unit 73 outputs a control signal to each of the head
drive unit 13 and the sensor body unit 22. However, this is only an
example, and, for example, when an instruction to measure the shape
of the workpiece 3 is received from the outside, the coordinate
value setting unit 73 may output a control signal to each of the
head drive unit 13 and the sensor body unit 22.
[0107] As an alternative, the coordinate value setting unit 73 may
output a control signal to each of the head drive unit 13 and the
sensor body unit 22 in accordance with a program stored in an
internal memory.
[0108] In above-described Embodiment 1, the machine tool includes
the machining unit 10 for feeding cutting oil to a work surface 3a
of the workpiece 3 and machining the work surface 3a, and is
configured to include the optical sensor unit 20 for dividing light
outputted from the frequency sweep light source 31a for outputting
light whose frequency varies periodically into irradiation light
with which the workpiece 3 is to be irradiated and reference light,
irradiating the workpiece 3 with the irradiation light, detecting a
peak frequency of interference light between reflected light which
is irradiation light reflected by the workpiece 3, and the
reference light, and measuring the distance from the machine tool
to the work surface 3a on the basis of the peak frequency, and the
shape calculation unit 75 for calculating the shape of the
workpiece 3 on the basis of the distance measured by the optical
sensor unit 20. Therefore, the machine tool can measure the shape
of the workpiece 3 even when the cutting oil remains on the work
surface 3a of the workpiece 3.
Embodiment 2
[0109] In the machine tool of Embodiment 1, the configuration is
provided in which the sensor head unit 21 of the optical sensor
unit 20 is mounted on the head body unit 11a. On the other hand, in
Embodiment 2, a machine tool is configured in such a way that a
sensor head unit 21b is mounted on a spindle lib. FIG. 13 is a
schematic diagram showing the machine tool according to Embodiment
2. In FIG. 13, because the same reference signs as those shown in
FIG. 1 denote the same components or like components, an
explanation of the components will be omitted hereinafter.
[0110] In FIG. 13, the spindle 11b of a machining head 11
attachably/detachably holds a machining tool 12 or the sensor head
unit 21b. Concretely, when a workpiece 3 is machined, a machining
tool 12 is held by the spindle 11b, and when the shape of the
workpiece 3 is measured, the sensor head unit 21b is held by the
spindle 11b, as shown in FIG. 13.
[0111] FIG. 14 is a schematic diagram showing the sensor head unit
21b of Embodiment 2. In FIG. 14, the sensor head unit 21b includes
a cylindrical-shaped housing 110. The sensor head unit 21b includes
two aspheric lenses 111 and 112 as a condensing optical element 35,
and a mirror 113 for changing the angle of light emitted from the
previous-stage aspheric lens 111 toward the next-stage aspheric
lens 112. Further, amounting portion 114 for mounting an optical
fiber which is an optical transmission unit 23 is disposed on a
side surface of the housing 110.
[0112] Because the mounting portion 114 is disposed on the side
surface of the housing 110 as described above, irradiation light
can be guided to the aspheric lenses 111 and 112 which are the
condensing optical element even in a state in which the sensor head
unit 21b is fixed to the spindle lib. Further, because the mirror
113 is disposed, the irradiation light incident from the side
surface can be made parallel to the central axis of the head body
unit 11a and applied to the workpiece 3.
[0113] In above-described Embodiment 2, the machine tool is
configured in such a way that the sensor head unit 21b is mounted
on the spindle 11b. Therefore, the machine tool can hold the sensor
head unit 21b by using a chuck device which the spindle 11b has.
Therefore, the machine tool can be produced at a low cost without
separately disposing a holding mechanism in order to mount the
sensor head unit 21b to the machining head 11.
Embodiment 3
[0114] In Embodiment 3, a machine tool includes a tool storage unit
100 for storing multiple machining tools 12 used for machining a
work surface 3a. A sensor head unit 21b is also stored in the tool
storage unit 100. Then, at the time of machining, a spindle 11b
attachably/detachably holds one of the multiple machining tools 12
stored in the tool storage unit 100. At the time of shape
measurement, the spindle 11b holds a sensor head unit 21b stored in
the tool storage unit 100.
[0115] FIG. 15 is a schematic diagram showing the machine tool
according to Embodiment 3. In FIG. 15, because the same reference
signs as those shown in FIG. 13 denote the same components or like
components, an explanation of the components will be omitted
hereinafter. The tool storage unit 100 is a rack for storing both
the multiple machining tools 12 used for machining the work surface
3a, and the sensor head unit 21b.
[0116] A tool replacement unit 101 has a mechanism for replacing
the machining tool 12 held by the spindle 11b. At the time of
machining, the tool replacement unit 101 selects one of the
multiple machining tools 12 stored in the tool storage unit 100,
and causes the spindle 11b to hold the selected machining tool 12.
On the other hand, at the time of shape measurement, the tool
replacement unit 101 selects the sensor head unit 21b stored in the
tool storage unit 100, and causes the spindle 11b to hold the
selected sensor head unit 21b. Because the mechanism for replacing
a machining tool 12 and the sensor head unit 21b is well known, a
detailed explanation will be omitted.
[0117] In above-described Embodiment 3, the machine tool is
configured in such a way that the sensor head unit 21b is stored in
the tool storage unit 100 for storing the machining tools 12.
Therefore, the machine tool can be produced at a low cost without
separately disposing a storage unit in order to store the sensor
head unit 21b.
[0118] Further, because the sensor head unit 21b stored in the tool
storage unit 100 is configured so as to be held by the spindle 11b,
the sensor head unit 21b can be handled in the same way that each
machining tool 12 is handled. Therefore, the machine tool can be
produced at a low cost without separately disposing a holding
mechanism in order to mount the sensor head unit 21b to the spindle
lib.
Embodiment 4
[0119] In Embodiment 3, the machine tool is configured in such a
way that the spindle 11b holds the sensor head unit 21b at the time
of measuring a shape. On the other hand, in Embodiment 4, a spindle
11b is configured so as to hold an optical sensor unit 20 at the
time of measuring a shape.
[0120] FIG. 16 is a schematic diagram showing a machine tool
according to Embodiment 4. As shown in FIG. 16, the optical sensor
unit 20 has a sensor head unit 21 and a sensor body unit 22. An
electric connection between the optical sensor unit 20 and a
machining head 11 will be explained using FIG. 17. FIG. 17 is a
partly enlarged view showing the machine tool according to
Embodiment 4. As shown in FIG. 17, the optical sensor unit and the
spindle 11b have electric connection portions 121 and 122,
respectively. The electric connection portions 121 and 122 are
defined by, for example, the interface standard in Recommended
Standard 232 (RS-232).
[0121] A communication cable 25 for transmitting and receiving
pieces of information containing distance information, a control
signal, and a synchronization signal, which are described before,
is connected to the electric connection portion 122 which the
spindle 11b has. The communication cable is passed through the
insides of the spindle 11b and a head body unit 11a, is led out of
the head body unit 11a, and is connected to a control unit 50.
Therefore, the machine tool of Embodiment 4 makes it possible to
perform transmission and reception of a signal between the control
unit 50 and the optical sensor unit 20 through a connection between
the electric connection portion 122 of the spindle 11b and the
electric connection portion 121 of the optical sensor unit 20.
[0122] Returning to FIG. 16, a tool storage unit 102 is a rack for
storing both multiple machining tools 12 used for machining a work
surface 3a, and the optical sensor unit 20. A tool replacement unit
101 has a mechanism for replacing the machining tool 12 held by the
spindle 11b. At the time of machining, the tool replacement unit
101 selects one of the multiple machining tools 12 stored in the
tool storage unit 102, and causes the spindle 11b to hold the
selected machining tool 12. On the other hand, at the time of shape
measurement, the tool replacement unit 101 selects the optical
sensor unit 20 stored in the tool storage unit 102, and causes the
spindle 11b to hold the selected optical sensor unit 20.
[0123] In FIGS. 16 and 17, the same reference signs as those shown
in FIG. 15 denote the same components or like components.
[0124] In above-described Embodiment 4, the machine tool is
configured in such a way that the optical sensor unit 20 is stored
in the tool storage unit 102 for storing the machining tools 12.
Therefore, the machine tool can be produced at a low cost without
separately disposing a storage unit in order to store the optical
sensor unit 20.
[0125] Further, because the optical sensor unit 20 stored in the
tool storage unit 102 is configured so as to be held by the spindle
11b, the optical sensor unit 20 can be handled in the same way that
each machining tool 12 is handled. Therefore, the machine tool can
be produced at a low cost without separately disposing a holding
mechanism in order to mount the optical sensor unit 20 to the
spindle 11b.
[0126] In addition, because the communication cable 25 between the
control unit 50 and the optical sensor unit 20 is configured so as
to be passed through the inside of the head body unit 11a, the
communication cable 25 can be prevented from being broken when the
machining head 11 moves.
[0127] In the machine tool according to Embodiments 1 to 4, the
machining unit 19 feeds cutting oil to the work surface 3a of the
workpiece 3.
[0128] However, as the oil which the machining unit 19 feeds to the
work surface 3a, any liquid used for, as a main purpose, the
prevention of the wearing away of a tool, the wearing away being
accompanied by metal processing, or the prevention of rise in the
temperature of a tool, the temperature rise being accompanied by
metal processing, can be used, and is not limited to cutting oil.
The liquid used for such a main purpose is called machining oil,
and cutting oil is included in the machining oil. Electric
discharge oil which will be mentioned later, or the like is
included in the machining oil.
[0129] Embodiment 5.
[0130] In Embodiments 1 to 4, the machine tool having the optical
sensor unit 20 is explained.
[0131] In Embodiment 5, an electric discharge machining apparatus
having an optical sensor unit 20 will be explained.
[0132] FIG. 18 is a schematic diagram showing the electric
discharge machining apparatus according to Embodiment 5. In FIG.
18, because the same reference signs as those shown in FIG. 1
denote the same components or like components, an explanation of
the components will be omitted hereinafter.
[0133] The electric discharge machining apparatus shown in FIG. 18
measures the distance from the electric discharge machining
apparatus to a work surface 3a by using an electrode 15 mounted on
a machining head 11, and calculates the shape of a workpiece 3 on
the basis of the measured distance.
[0134] A vice 2' is a fixture for fixing the workpiece 3 so that
the workpiece 3 does not move at the time of machining the
workpiece 3.
[0135] A work tank 4 is a container for storing electric discharge
oil 5 which is machining oil. Each of a table 1 and the workpiece 3
is contained in the work tank 4 in such a way that the whole of
each of the parts is immersed in the electric discharge oil 5.
[0136] The electrode 15 is mounted on an outer surface 11c facing
the table 1, out of multiple outer surfaces which a head body unit
11a has. The electrode 15 has a leading end portion 15a from which
the electrode emits electrons. By applying a voltage between the
leading end portion 15a and the work surface 3a of the workpiece 3,
the electrode 15 causes sparks to occur by means of electric
discharge. Because the work surface 3a is scraped by the occurrence
of sparks, machining of the workpiece 3 can be performed. As the
electrode 15, a high-conductivity material such as copper or
graphite is used.
[0137] Also in the electric discharge machining apparatus shown in
FIG. 18, the optical sensor unit 20 calculates the distance from a
leading end 21a of a sensor head unit 21 to the work surface 3a of
the workpiece 3 and calculates the shape of the workpiece 3 on the
basis of the calculated distance, like in the machine tool shown in
FIG. 1.
[0138] When the optical sensor unit 20 calculates the distance, the
sensor head unit 21 applies irradiation light outputted from a
sensor body unit 22 to the work surface 3a, like that of Embodiment
1. The sensor head unit 21 receives reflected light containing both
reflected light which is irradiation light reflected by the work
surface 3a and reflected light which is irradiation light reflected
by the electric discharge oil 5. The sensor head unit 21 outputs
the reflected light received thereby to the sensor body unit
22.
[0139] When a machining unit 10 machines the work surface 3a, the
whole of the workpiece 3 needs to be immersed in the electric
discharge oil 5. On the other hand, when the optical sensor unit 20
calculates the distance, it does not matter whether or not the work
surface 3a of the workpiece 3 is immersed in the electric discharge
oil 5. Therefore, the optical sensor unit may calculate the
distance in a state in which the work surface 3a of the workpiece 3
is not immersed in the electric discharge oil 5, by moving the
table 1 in the negative direction of the z axis using an actuator
or the like which is not illustrated.
[0140] In above-described Embodiment 5, the electric discharge
machining apparatus includes the machining unit 10 for machining
the work surface 3a of the workpiece 3 immersed in machining oil,
and is configured so as to include: the optical sensor unit 20 for
dividing light outputted from a frequency sweep light source 31a
for outputting light whose frequency varies periodically within a
single frequency band into irradiation light with which the
workpiece 3 is to be irradiated and reference light, irradiating
the workpiece 3 with the irradiation light, detecting a peak
frequency of interference light between reflected light which is
irradiation light reflected by the workpiece 3, and the reference
light, and measuring the distance from the electric discharge
machining apparatus to the work surface 3a on the basis of the peak
frequency; and a shape calculation unit 75 for calculating the
shape of the workpiece 3 on the basis of the distance measured by
the optical sensor unit 20. Therefore, the electric discharge
machining apparatus can measure the shape of the workpiece 3 even
when the machining oil remains on the work surface 3a of the
workpiece 3.
[0141] It is to be understood that any combination of two or more
of the above-described embodiments can be made, various changes can
be made in any component according to any one of the
above-described embodiments, or any component according to any one
of the above-described embodiments can be omitted within the scope
of the present invention.
INDUSTRIAL APPLICABILITY
[0142] The present invention is suitable for machine tools and
electric discharge machining apparatuses which machine a work
surface of a workpiece.
REFERENCE SIGNS LIST
[0143] 1 table, 2, 2' vice, 3 workpiece, 3a work surface, 4 work
tank, 5 electric discharge oil, 10 machining unit, 11 machining
head, 11a head body unit, 11b spindle (tool holding unit), 11c
outer surface, 12 machining tool, 13 head drive unit, 14 cutting
oil nozzle, 15 electrode, 15a leading end portion, 20 optical
sensor unit, 21, 21b sensor head unit, 21a leading end, 22 sensor
body unit, 23 optical transmission unit, 25 communication cable, 31
frequency sweep light output unit, 31a frequency sweep light
source, 32 optical dividing unit, 33 optical coupler, 34
circulator, 35 condensing optical element, 36 optical interference
unit, 37 optical interferometer, 38 optical detector, 39 A/D
converter, 40 distance calculation unit, 50 control unit, 61
memory, 62 processor, 71 input unit, 72 storage device, 73
coordinate value setting unit, 74 cutting oil feed unit, 75 shape
calculation unit, 76 error calculation unit, 77 display processing
unit, 78 three-dimensional data conversion unit, 79 display, 81
coordinate value setting circuit, 82 cutting oil feed circuit, 83
shape calculation circuit, 84 error calculation circuit, 85
three-dimensional data conversion circuit, 91 memory, 92 processor,
100, 102 tool storage unit, 101 tool replacement unit, 110 housing,
111, 112 aspheric lens, 113 mirror, 114 mounting portion, and 121,
122 electric connection portion.
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